The present invention relates to a process of correction of design data for the production of photomask coping with miniaturization and high-density of semiconductor. Particularly, the present invention relates to a method for correcting original figure data used in the pattern exposure system for forming a pattern of photomask as to obtain the objective shape of pattern on a wafer.
Recently, from a tendency for electric equipment to be made highly functional and lighter, thinner, shorter and smaller, it is being desired more and more that several LSI""s typified by ASIC (application specific integrated circuit) are made highly integrated and highly functional. Namely, to realize the high function is desired for LSI such as ASIC by reducing the size of chip.
The process for forming semiconductor device is made through several steps in such a manner that figure data for forming photomask pattern (it is also called xe2x80x9cpattern dataxe2x80x9d are made through function design, logical design, circuit design, layout design and others, a photomask is produced using the figure data, thereafter the pattern of photomask is transferred on a wafer by the pattern reduction exposure, so that the above-mentioned LSI such as ASIC is produced.
In general, a photomask is made through several steps in such a manner that pattern exposure is given to photosensitive resist disposed on the shielding film of a photomask substrate for (the shielding film of photomask substrate is also called xe2x80x9cphotomask blankxe2x80x9d) using the above-mentioned figure data (xe2x80x9cpattern dataxe2x80x9d) and by means of the electron beam pattern exposure system or the photo pattern exposure system projecting rays such as excimer wavelength, steps such as development and etching are made, by which a photomask is produced.
Namely, ionizing radiation is applied to given areas of photosensitive resist is coated on a shielding metallic thin film of photomask substrate provided on one side of glass substrate and dried, by means of the pattern exposure system, by which a latent image is formed. Then, the photosensitive resist having latent image is developed, by which a resist pattern with a desired shape is formed corresponding to the irradiation area of ionizing radiation. Thereafter, the metallic film is worked following the resist pattern by etching using the resist pattern as etching-proof resistance resist so that a photomask with a desired metallic film pattern is obtained.
In case of a pattern of photomask being transferred to a wafer by reduction exposure, a photomask is also called a reticule pattern.
When a pattern of photomask is transferred to a wafer by reduction exposure, a distortion of the shape of exposure called optical proximity effect is appeared. The reason because when a size of the shape of exposure (a size of pattern exposure to wafer) approaches wavelength of exposure light or becomes smaller than wavelength of light, exposure faithful to the shape of pattern of photomask becomes impossible by the phenomenon of diffraction so that the shape of pattern of photomask exposed to the wafer distortion is distorted on a wafer.
In a case where a pattern of photomask (the shape of part of photomask not transmitting light) has the shape as shown in FIG. 8A(i), the shape formed on a wafer becomes as shown in FIG. 8A(ii). Therefore, when it is desired to obtain the shape of pattern on a wafer as shown in FIG. 8A(i), a pattern of photomask (the shape of part of photomask not transmitting light) is corrected as shown in FIG. 8B(i) so that the shape of pattern formed on a wafer is made as shown in FIG. 8B(ii). Such a correction made in consideration of the influence of diffraction of light is called OPC (Optical Proximity Correction).
Hereafter, as to figure data for forming a pattern of photomask, data not having the correction made in consideration of distortion (deformation) when producing a mask and when producing a wafer according to the circuit design is called original figure data of design data, or original figure data. Further, data having the correction made in consideration of distortion (deformation) when producing a mask and when producing a wafer is called correction figure data. In general, the process for carrying out the optical proximity correction given to original figure data is called the OPC process, and correction data in which original figure data is corrected through the optical proximity correction is also called the OPC process data. Figure data is also called pattern data Figure data for forming a pattern of photomask is formed according to various information, which is expressed in the X-Y coordinates.
Referring to FIGS. 4 and 5, a first conventional example of a method for generating correction figure data is explained. Further, referring to FIGS. 6 and 7, a second conventional example of a method for generating correction figure data is explained.
FIG. 4 is a flow sheet of a first conventional example for generating correction figure data. FIG. 5A(i) and FIG. 5B(i) show an example of original figure data. In case of the example shown in FIG. 5A(i), correction is needed for corners of figure. In case of the sample shown in FIG. 5 B(i), correction is needed for parts of figure in which the parts are arranged sparsely.
FIG. 5A(ii) and FIG. 5B(ii) show patterns in which correction figures are generated for original figure data shown in FIG. 5A(i) and FIG. 5B(i) according to the first conventional method, respectively. FIG. 5A(iii) and FIG. 5B(iii) show patterns transferred to wafers (hereafter called xe2x80x9cwafer patternsxe2x80x9d) through photomasks having the shapes of pattern shown in FIG. 5A(ii) and FIG. 5B(ii), respectively.
FIG. 6 is a flow sheet of the second conventional method for generating correction figure data. FIG. 7A(i) and FIG. 7B(i) show original figure data, respectively. FIG. 7A(ii) and FIG. 7B(ii) show patterns in which correction figures are generated according to the second conventional method. FIG. 7A(iii) and FIG. 7B (iii) show patterns transferred to wafers through photomasks produced by patterns shown in FIG. 7A(ii) and FIG. 7B(ii), respectively.
Hereafter, to make this description plain, original figure data shown in FIG. 5A(i) and FIG. 5B(i) are made the same as original figure data shown in FIG. 7A(i) and FIG. 7B(i).
Further, xe2x80x9cS410xe2x80x9d to xe2x80x9cS490xe2x80x9d in FIG. 4 and xe2x80x9cS610xe2x80x9d and xe2x80x9cS670xe2x80x9d in FIG. 6 designate steps of process.
The first conventional method is a method for determining the correction figure data for optical proximity correction according to the information on deformation generated when original figure data is transferred to a wafer by optical proximity effect.
The production of photomask is carried out using figure data in which only the optical proximity correction process (OPC process) is given to original figure.
This method is based on the assumption that the faithfulness or correctness of pattern formed on a photomask to original pattern can be kept. Namely, slight difference is generated between original figure data and a pattern formed on a photomask in the production. However, heretofore, it was thought that patterns to be formed are not small so far so that the influence on quality brought about by the difference between the two can neglected.
In this case, patterns (figures) determined according to the information on deformation when forming original figure patterns by optical proximity effect obtained in advance, in this example, a figure of square is generated at corners of original figure data shown in FIG. 5B(i). On the other hand, the figures for correcting the phenomenon that width of parts of original figure data as shown in FIG. 5B(i) in which the parts are disposed sparsely becomes thin are generated.
When a pattern is transferred to a wafer through the photomask produced using pattern data with the above-mentioned figures for correcting to the phenomenon, patterns (figures) shown in FIG. 5A(iii) and FIG. 5B(iii) are formed on a wafer.
However, recently, the miniaturization and high-density of mask pattern accompanied by the miniaturization and high-density forming of wafer pattern progresses further so that the faithfulness of a pattern formed on a photomask to original figure data, set heretofore as a premise, comes to not be kept. Therefore, the necessity for the consideration of the influence of the difference between original figure data and a pattern formed on a photomask, which difference will affect a wafer pattern formed on a wafer, was appeared.
Accordingly, in the second conventional method, the faithfulness of a photomask to original figure data is kept by further giving the correction made in consideration of distortion (deformation) in the production of photomask to the figure data in which only the process of optical proximity correction process (OPC process) is given to original figure data.
In the second method, when forming a photomask on a glass substrate, further correction pattern determined according to the information on deformation of the shape of pattern in contrast to the original figure data, according to the shape of pattern and the arrangement thereof, is added to the corrected pattern shown in FIG. 5.
Correction pattern is added to corners of correction pattern (correction FIG. 521) is shown in FIG. 5A(ii) and FIG. 5B(ii) in consideration of distortion (deformation) in the production of photomask, and further, the correction for edges is added to the figure for correcting the phenomenon that a width of parts in which the parts are arranged sparsely become thin, by which the correction figure pattern can be obtained as shown in FIG. 7(A)(ii) and FIG. (B)(ii).
However, in the present conditions where produced LSI is made high-density and the amount of figure data included in design data is increased rapidly, there is a tendency for a time taken for the process for such a correction pattern to be increased.
Therefore, if the correction pattern is applied to original figure pattern according the first conventional method and further another correction is applied to the corrected figure pattern, the process cannot be carried out within practical processing time. As a result, data size for producing a photomask becomes impractical.
Namely, the first conventional method has a problem that the faithfulness of a photomask actually formed to original figure pattern is lost. The second conventional method has a problem that many resources are needed for producing devices such as a computer for generating corrected pattern, a pattern exposure system, and therefore this method is not a practical method.
As above-mentioned, under a circumstance that miniaturization and high-density of mask pattern is further progressed recently, the necessity for consideration to be given to that the difference between original figure data and a pattern formed on a photomask influences a wafer pattern formed on a wafer came out. Therefore, it was desired to cope with the aforementioned necessity was obtained.
The present invention aims at the provision of a process for making mask pattern data which is the correction data in which original figure data is corrected, for forming a photomask, wherein the correction data makes possible to obtain the objective pattern on a wafer, in the middle of miniaturization and high-density of mask F74 pattern being progressed recently.
At the same time, the present invention aims the provision of a process for making photomask pattern data, which makes possible for process to be carried out in practical processing time without the proposed (conventional) data of tremendous amount to be processed.
A process for making photomask pattern of the present invention is a process for making photomask pattern data in which correction pattern data obtained by correcting original figure data of design data used in the pattern exposure system for carrying out pattern exposure for forming a pattern of photomask in order to obtain the objective shape of pattern on a wafer is newly generated as the figure data for the pattern exposure system, wherein the method comprises the steps of: (a) a first step for fetching original data of design data as digital data; (b) a second step for extracting the information on distortion (deformation) of formed pattern of from the original figure data when producing a photomask using the original figure data; (c) a third step for extracting the information on the information on distortion (deformation) of formed pattern when producing a pattern on a wafer using the photomask; (d) a fourth step for obtaining the information for determining parts to be corrected and the amount of correction by combining the information obtained in the second step and the information obtained in the third step; and (e) a fifth step for generating the correction figure for correction applied to the original figure data of design data, on the basis of the information obtained in the fourth step, so that correction pattern data is obtained.
Further, in the above-mentioned process for making photomask pattern data, in the third step, the amount of distortion (deformation) by diffraction of light at several parts when transferring a mask pattern with the same shape as original figure pattern on a wafer is extracted, by the comparison of a measurement of wafer after a test of transferring of a pattern on a wafer using a test photomask with the test photomask or by simulation, which extracted data of the amount of distortion can be used as the information on distortion (deformation) of formed pattern.
A photomask of the present invention is a photomask formed through pattern exposure, developing, and etching, using the correction pattern data obtained by correcting original figure data of design data used in the pattern exposure system for carrying out pattern exposure for a pattern of photomask in order to obtain the objective shape of pattern on a wafer, characterized in that the photomask is formed using the correction pattern data made according to the above-mentioned process for making photomask pattern data.
A process for making photomask pattern data of the present invention enables the provision of a process for making photomask pattern data for making photomask pattern data for forming photomask, in which the objective shape of pattern can be obtained on a wafer under such a circumstance that miniaturization and high-density of mask pattern is progressed.
At the same time, the present invention aims at the provision of a process for making photomask pattern data which data enables the process in practical processing time without the proposed (conventional) data of tremendous amount to be processed.
Concretely, this is achieved by a process for making photomask pattern data in which correction pattern data obtained by correcting original figure data of design data used in the pattern exposure system for carrying out pattern exposure for forming a pattern of photomask in order to obtain the objective shape of pattern on a wafer is newly generated as the figure data for the pattern exposure system, wherein the method comprises the steps of: (a) a first step for fetching original data of design data as digital data; (b) a second step for extracting the information on distortion (deformation) of formed pattern of from the original figure data when producing a photomask using the original figure data; (c) a third step for extracting the information on the information on distortion (deformation) of formed pattern when producing a pattern on a wafer using the photomask; (d) a fourth step for obtaining the information for determining parts to be corrected and the amount of correction by combining the information obtained in the second step and the information obtained in the third step; and (e) a fifth step for generating the correction figure for correction against the original figure data of design data, on the basis of the information obtained in the fourth step, so that correction pattern data is obtained.
The third step enables to obtain relatively simply the amount of distortion (deformation) by diffraction of light, by extracting the amount of distortion (deformation) by diffraction of light at several parts when transferring a mask pattern with the same shape as original figure pattern on a wafer, by the comparison of a measurement of wafer after a test of transferring of a pattern on a wafer using a test photomask with the test photomask or by simulation, so that the extracted data is used as the information on distortion (deformation) of formed pattern.